Organisation

• What are the basic building blocks of life?

  Cells.
• What is a tissue?

  A group of cells with a similar structure and function.
• What is an organ?

  A group of different tissues working together to carry out a function.
• What is an organ system?

  A group of organs working together to carry out a function.
• What is an organism?


  A living thing made of organ systems working together.
• What is the digestive system?

  An organ system which works to digest food and absorb the nutrients into the bloodstream.
• What are enzymes?

  Catalysts, made of protein that speed up reactions. In the digestive system enzymes break down large molecules into small soluble ones.
• How do enzymes work?

  They have a specific active site that allows them to bind and react with specific substrate molecules.
• What is the "lock and key" theory?

  A simple model that shows enzymes as a lock, where only a substrate with the correct shape (key) will bind.
• What does optimum mean?

  The temperature or pH that allows the enzyme to work at it's fastest rate.
• What does denature mean?

  If the shape of the active site changes, no substrate can bind. The enzyme can no longer work when it's active site is denatured.
• What can denature an enzyme active site?

  Temperatures that are too high and extreme pH can both make the active site change shape and become denatured. This is permanent.
• Can low temperatures denature enzymes?

  No, the enzyme will not change shape if cold but has low kinetic energy so there will be a slower rate of reaction. This is reversible.
• What are the enzymes in digestion?

  Amylase (and other carbohydrases), protease and lipase.
• What does amylase do?

  It is a carbohydrase that breaks down starch into sugars. It is produced in the salivary glands (in the mouth).
• What do proteases do?

  Break down proteins into amino acids. They are produced in the stomach and pancreas.
• What do lipases do?

  Break down lipids (fats and oils) into fatty acids and glycerol. They are produced in the small intestine.
• What do carbohydrases do?

  Break down sugars into glucose. Amylase is a type of carbohydrase, but there are others in the small intestine too.
• What do we do with the digested products?

  Cells build new proteins, carbohydrates and lipids with the molecules we have digested. Some glucose is used in respiration too.
• What other chemicals are in the digestive system?

  Hydrochloric acid is found in the stomach and bile (made in the liver and stored in the gall bladder) is found in the small intestine.
• What does hydrochloric acid do?

  Kills some bacteria on the food we ate. Also provides the optimum pH for stomach enzymes (proteases) to work at a fast rate.
• What does bile do?

  Bile is alkaline, so neutralises hydrochloric acid. Also it emulsifies fat droplets, giving a larger surface area for lipase enzymes to work.
• What is a qualitative food test?

  A test that shows if a substance is there or not. A qualitative test doesn't give a measurement result, just a change of colour. It can be hard to decide if one food has more of a substance than another.
• What is the Benedict's test for sugars?

  When sugary food/drink is heated with Benedict's reagent, it turns from blue to brick red (or green). This shows sugar is present.
• What is the Biuret test for protein?

  When Biuret reagent is added to food/drink containing protein, it turns from pale blue to lilac. This shows protein is present.
• What is metabolism?

  The rate at which molecules are broken down during digestion and built into new molecules by cells. Sometimes called metabolic rate.
• What does the heart do?

  It is an organ that contracts to pump blood around the body and to the lungs. It is a double pump.
• Why is the heart called a double pump?

  The right ventricle pumps blood to the lungs for gas exchange. The left ventricle pumps blood to the rest of the body.
• What blood vessels must you label?

  Vena cava, aorta, pulmonary artery, pulmonary vein and coronary arteries.
• What lung structures must you label?

  Trachea, bronchi, alveoli, and capillaries around the alveoli.
• What controls resting heart rate?

  A group of cells in the right atrium acting as a pacemaker. Some people need an artificial pacemaker if their heart rate is irregular.
• What are the three types of blood vessel?

  Arteries (eg, aorta, coronary arteries and pulmonary artery), veins (eg, vena cava and pulmonary vein) and capillaries.
• Why do arteries have muscular/elastic walls?

  Arteries carry blood at high pressure, so they need to be elastic and muscular to cope with the surges of blood and smooth out the flow.
• Why do veins have thin walls and valves?

  Veins carry blood at low pressure so don't need thick walls. As the blood flows more slowly, valves stop blood flowing backwards.
• Why do capillaries have walls one cell thick?

  Molecules need to get in and out of the blood from the capillaries so the walls need to be very thin so diffusion can take place easily.
• What is blood made up of?

  A liquid called plasma, with red blood cells, white blood cells and platelets suspended in it.
• What do red blood cells do?

  Red blood cells contain many molecules of haemoglobin. Each haemoglobin carries oxygen molecules from the lungs to the cells.
• How are red blood cells adapted for their function?

  They have no nucleus, so more space for haemoglobin molecules, and also have a biconcave disc shape which makes them flexible to fit through narrow capillaries.
• What do white blood cells do?

  They destroy bacteria, produce antibodies and produce antitoxins.
• How are white blood cells adapted for their function?

  They have an irregular shape, and can change shape easily, so they can squeeze out of blood capillaries to reach pathogens when we are infected.